ChatGPT developed a goblin obsession after OpenAI tried to make it nerdy

Following the release of GPT-5.5 last week, people noticed something funny about OpenAI's latest model. In its Codex coding app, the company left a system prompt instructing GPT 5.5 to avoid mention of goblins, gremlins and other creatures. Yes, you read that right. "Never talk about goblins, gremlins, racoons, trolls, ogres, pigeons, or other animals or creatures unless it is absolutely and unambiguously relevant to the user's query," the prompt reads.

Apparently, enough people started talking about ChatGPT's creature obsession that OpenAI felt the need to provide an accounting of where the goblins came from. In a blog post published Wednesday, the company explains it began to notice a change in ChatGPT following the release of GPT-5.1 last November. After one safety researcher asked OpenAI to include the words "goblin" and "gremlin" in an investigation into the chatbot's verbal ticks, the company found ChatGPT's usage of "goblin" increased by 175 percent after the release of GPT-5.1. Meanwhile, "gremlin" usage had risen by 52 percent over that same period.

This is an actual line that was added to the official system prompt for Codex for GPT-5.5 by OpenAI. Usually the system prompt is as minimal as possible, so I assume it would otherwise mention goblins a lot.

— Ethan Mollick (@emollick.bsky.social) 2026-04-28T06:14:22.988Z

"A single 'little goblin' in an answer could be harmless, even charming. Across model generations, though, the habit became hard to miss: the goblins kept multiplying, and we needed to figure out where they came from," OpenAI says. After the release of GPT-5.4, the company (and some users) noticed an even bigger uptick in goblin references. At that point, an investigation was able to pinpoint what OpenAI describes as "the first connection to the root cause."

For a while now, ChatGPT has included a personality feature that allows users to customize the style and tone of the chatbot's responses. Prior to March of this year, one option people could select was "nerdy." Part of the system prompt for that personality read as follows: "The world is complex and strange, and its strangeness must be acknowledged, analyzed, and enjoyed. Tackle weighty subjects without falling into the trap of self-seriousness."

When OpenAI mapped goblin mentions to different ChatGPT personalities, it found the nerdy personality was disproportionately responsible for using that one word. Despite only accounting for 2.5 percent of all ChatGPT responses, it made 66.7 percent of all goblin mentions generated by the chatbot. Further investigation revealed tha